Plasma processing container internal member and production method thereof

ABSTRACT

It is to propose an internal member for a plasma treating vessel having excellent resistances to chemical corrosion and plasma erosion under an environment containing a halogen gas and an advantageous method of producing the same, which is a member formed by covering a surface of a substrate with a multilayer composite layer consisting of a metal coating formed as an undercoat, Al 2 O 3  film formed on the undercoat as a middle layer and Y 2 O 3  sprayed coating formed on the middle layer as a top coat.

TECHNICAL FIELD

[0001] This invention relates to an internal member for plasma-treatingvessel having an excellent resistance to plasma erosion and a method ofproducing the same.

[0002] Particularly, the invention is a technique capable of applying tomembers used in a plasma treatment under a plasma environment using atreating gas containing a halogen element such as deposit shield, baffleplate, focus ring, insulator ring, shield ring, bellows cover, electrodeand so on.

[0003] Moreover, the invention is applicable to internal parts forplasma-treating vessels in a field of a semiconductor manufacturingdevice, a manufacturing apparatus for a liquid crystal device or thelike.

BACKGROUND ART

[0004] In general, a fluoride such as BF₃ or NF₃, a chloride such asBCl₃ or SnCl₄, a bromide such as HBr, or the like is used as a treatinggas for various treatments in the manufacturing process ofsemiconductors, liquid crystal devices and the like, so that there is aproblem that parts in the treating vessel are considerably corroded anddamaged.

[0005] For instance, as a material used in the plasma-treating vesselfor the semiconductor manufacturing apparatus, there are known ametallic material such as Al, Al alloy or the like, an anodized oxidefilm of Al covering the surface of the metallic material, a sprayedcoating such as boron carbide or the like, a sintered body film ofAl₂O₃, Si₃N₄ or the like, and a high polymer film of fluorine resin,epoxy resin or the like. These materials are known to be subjected to achemical damage when being contacted with a halogen ion indicating astrong corrosive property, or to an erosion damage through finesparticles of Sio₂ and Si₃N₄ and an ion excited by a plasma.

[0006] Especially, a plasma is frequently used for more activating thereaction in the process using a halogen compound. However, the halogencompound is dissociated to atomic F, Cl, Br, I or the like indicating avery strong corrosive property under an environment using such a plasma.Even in this case, if a finely divided solid of SiO₂, Si₃N₄, Si, W orthe like is existent in such an environment, the member used in theplasma-treating vessel is strongly subjected to not only the chemicalcorrosion but also the erosion damage through the above fine particles.

[0007] And also, the environment excited by the plasma is ionized evenby a gas having no corrosive property such as Ar gas to cause aphenomenon of strongly impinging to a solid face (ion bombardment), sothat various members arranged in the above vessel are subjected to astronger damage.

[0008] Heretofore, there was a method of forming a thin Al₂O₃ film orthe like as a technique adopted when being subjected to such a chemicalcorrosion or erosion damage. However, such a technique has the followingproblems.

[0009] (1) With respect to a material covered with Al₂O₃ film (alumite)by subjecting Al and Al alloy to an anodization to provide corrosionresistance, there is a problem that the service life becomes shorterwhen being subjected to plasma erosion in an environment containing ahalogen gas. And also, since it is an Al-containing film, AlF₃ particlesare created, which bring about a fear of degrading quality ofsemiconductor product manufactured.

[0010] (2) There is a technique that a dense film of oxide, carbide,nitride, fluoride or the like of Group 3a element in the Periodic Tablesuch as Sc, Y, La, Ce, Yb, Eu, Dy or the like is formed on the surfaceof a part through PVD or CVD process, or a single crystal of Y₂O₃ isapplied thereto (JP-A-10-4083). However, this technique has problemsthat the film forming rate is slow and the productivity is poor andplural film members (composite film) can not simultaneously be formed.

[0011] It is, therefore, an object of the invention to propose asurface-treated member for plasma-treating vessel or the like havinglarge resistances to damage due to chemical corrosion and damage throughplasma erosion under environment containing a halogen gas as well as amethod of producing the same.

DISCLOSURE OF THE INVENTION

[0012] The invention solves the aforementioned problems and drawbacks ofthe conventional techniques by adopting means as mentioned below. Thatis, the construction of the invention is as follows:

[0013] (1) A cover member comprising a substrate and a layer of Y₂O₃sprayed coating having a porosity of 0.2-10% and a thickness of 50-2000μm formed on a surface of the substrate through a thermal sprayingprocess.

[0014] (2) A cover member comprising a substrate, and a composite layerconsisting of a coating of one or more metals or alloys selected from Niand an alloy thereof, W and an alloy thereof, Mo and an alloy thereofand Ti and an alloy thereof, which are excellent in an adhesion propertyto Y₂O₃ sprayed coating, formed at a thickness of 50-500 μm as anundercoat on a surface of the substrate under a plasma generatingcondition in an environment containing a halogen compound through,preferably, a thermal spraying process and a Y₂O₃ sprayed coating formedat a thickness of 50-2000 μm on the undercoat in case of an environmenthaving a strong corrosion property.

[0015] (3) A cover member comprising a substrate and a multilayercomposite layer consisting of the above metal coating (preferablysprayed coating) formed on a surface of the substrate as an undercoat, aAl₂O₃ coating (preferably sprayed coating) formed on the undercoat as amiddle layer and the above Y₂O₃ sprayed coating formed on the middlelayer as a topcoat through thermal spraying in case of an environmenthaving a strong corrosion property.

[0016] (4) A cover member comprising a substrate and a multilayercomposite layer consisting of the above metal coating (preferablysprayed coating) formed on a surface of the substrate as an undercoat, afilm of Al₂O₃ and Y₂O₃ (preferably sprayed coating) formed on theundercoat as a middle layer and the above Y₂O₃ sprayed coating formed onthe middle layer as a topcoat through thermal spraying in case of anenvironment having a strong corrosion property.

[0017] (5) A cover member is covered with the Y₂O₃ sprayed coatingdirectly formed on the surface of the substrate or indirectly formedthrough the undercoat or middle layer in the above method, wherein thesprayed coating is obtained by using Y₂O₃ powder having a purity of notless than 95% and adopting a spraying method selected fromplasma-spraying the powder in air, plasma-spraying in an Ar gascontaining no oxygen under a reduced pressure, high-speed flamespraying, explosion spraying and the like.

[0018] Among them, the method of plasma-spraying under the reducedpressure of Ar gas is also effective for the improvement of thecorrosion resistance.

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] The inventors have made studies in order to solve theaforementioned problems of the conventional techniques and confirmedthat the damage of the internal member for the plasma-treating vessel isa damage due to chemical corrosion through a halogen gas and a damagedue to plasma erosion. And also, it has been found that when the memberis used in an environment containing the halogen excited by the plasma,it is important to prevent the damage caused by the resistance to theplasma erosion, which is then effective to prevent the chemicalcorrosion.

[0020] To this end, the inventors have made mainly the formation of thecoating effective for the resistance to plasma erosion. As a result, theabove member according to the invention is developed.

[0021] That is, the invention adopted as means for solving the abovesubject is fundamentally a member obtained by forming a sprayed coatingconsisting of only Y₂O₃ on a surface of a substrate such as metal,ceramic, carbon material or the like through thermal spraying process.In case of a strong corrosive environment using the above member, thereis developed a member obtained by forming an undercoat of a metal havinga strong resistance to halogen gas corrosion beneath the above Y₂O₃sprayed coating and further forming a middle layer of Al₂O₃ or Y₂O₃.

[0022] The construction of the member according to the invention isdescribed in detail below.

[0023] (1) Substrate

[0024] As a substrate for forming the sprayed coating, various steelsinclusive of stainless steel, aluminum and aluminum alloy, tungsten andtungsten alloy, titanium and titanium alloy, molybdenum and molybdenumalloy, carbon and oxide or non-oxide ceramic sintered body, acarbonaceous material and the like are favorable.

[0025] Moreover, copper and copper alloy are unfavorable because theyare subjected to plasma erosion or corrosion through a halogen compoundto bring about environmental contamination. Therefore, if the use ofcopper or copper alloy is required in view of apparatus construction,they are required to be covered with Cr, Ni or the like by electrolyticplating, chemical plating, vapor deposition or the like.

[0026] (2) Construction of Sprayed Coating

[0027] The sprayed coating is preferable to be formed on the surface ofthe substrate by subjecting the substrate to a shot blast treatment andthen directly thermal spraying Y₂O₃, or by forming a film or sprayedcoating of a metal material having a strong resistance to corrosionthrough a halogen gas as an undercoat layer on the surface of thesubstrate by PVD treatment, CVD treatment or thermal spraying treatmentand then spraying Y₂O₃ powder on the undercoat as a top coat. In thelatter case, the film thickness of the metal undercoat (sprayed coatingor the like) is within a range of 50-500 μm. When the undercoat layer isthinner than 50 μm, the action and effect as the undercoat become weak,while when it exceeds 500 μm, the effect is saturated and there is nomeaning on the thickening.

[0028] As the metal material for the undercoat, nickel and nickel alloy,tungsten and tungsten alloy, molybdenum and molybdenum alloy, titaniumand titanium alloy and so on are preferable.

[0029] On the other hand, the Y₂O₃ sprayed coating as a top coat isfavorable to have a thickness of 50-2000 μm even when it is directlyformed on the surface of the substrate or when it is sprayed onto theundercoat to form a composite layer or further when Al₂O₃ or Al₂O₃+Y₂O₃coated film is formed as a middle layer. Because, when the thickness isless than 50 μm, the effect on the prevention of the damage due to theplasma erosion is poor, while when it exceeds 2000 μm, the effect issaturated and there is no meaning in the economical reason.

[0030] Moreover, the porosity of the Y₂O₃ sprayed coating as a top coatis preferably within a range of 0.5-10%. It is difficult to produce thesprayed coating having the porosity of less than 0.5% by the sprayingmethod, while the coating having the porosity of more than 10% is poorin the corrosion resistance and the resistance plasma erosion.

[0031] (3) Y₂O₃ Sprayed Coating as an Outermost Layer on Member

[0032] A most characteristic construction of the invention lies in thatY₂O₃ is adopted as a material indicating the resistance to plasmaerosion in an environment containing a halogen gas and formed as asprayed coating layer as a structure of an outermost surface layer ofthe substrate. As a result of the inventors' studies, it has been foundthat since Y₂O₃ has a specific gravity of 4.84 and a melting point of2410° C. and is strong in the chemical bonding force to oxygen, itmaintains a stable state even if the action of plasma erosion issuffered in the atmosphere containing the halogen gas. In this case,however, it is required to use Y₂O₃ having a purity of not less than95%. If an impurity such as Fe, Mg, Cr, Al, Ni, Si or the like iscontained as an oxide, the erosion resistance is unfavorably lowered.The purity is more favorable to be not less than 98%.

[0033] Moreover, Al₂O₃ as a middle layer formed just beneath the Y₂O₃sprayed coating is chemically stable and less in the change underenvironment of plasma spraying at atmospheric pressure or plasmaspraying under a reduced pressure and serves to compensate theresistance to plasma erosion of Y₂O₃.

[0034] (4) Coating Method

[0035] a. Formation of Sprayed Coating

[0036] In the invention, Y₂O₃ coating as a top coat in at leastoutermost layer is a sprayed coating. Further, it is preferable that thewhole structure of the coating is rendered into the following multilayerstructure in order to strengthen the sprayed coating of the top coat.

[0037] That is, an undercoat of a metal sprayed coating is formed on thesurface of the substrate and Al₂O₃ sprayed coating or a mixture sprayedcoating of Al₂O₃ and Y₂O₃ in the gradient compounding is formed thereonas a middle layer and further Y₂O₃ sprayed coating is formed thereon asa top coat.

[0038] The reason why the above coating structure is preferable is dueto the fact that by forming as the middle layer Al₂O₃ having excellentcorrosion resistance and resistance to plasma erosion as compared withthe metal sprayed coating is rendered the sprayed coating into amultilayer structure, and the through-holes of the coating is decreasedto improve the corrosion resistance and the resistance to erosion.Furthermore, Al₂O₃ as the middle layer develops good adhesion propertyto both of the undercoat and the top coat. In this meaning, the middlelayer is favorable to be a mixture layer of Al₂O₃ and Y₂O₃. In thiscase, the mixture layer is favorable to be based on the gradientcompounding that the Al₂O₃ concentration at the undercoat side becomeshigh and the Y₂O₃ concentration at the top coat side becomes high. Theformation of such a middle layer can easily be carried out by adopting aspraying process, so that it is said to be a preferable embodiment thatthe middle layer is formed as a sprayed coating. Moreover, the thicknessof the middle layer is favorable to be within the same range as the Y₂O₃sprayed coating of the top coat.

[0039] In the invention, a plasma spraying process under an atmosphericpressure or a plasma spraying process in an atmosphere containingsubstantially no oxygen is favorable for forming a sprayed coating ofmetal or Al₂O₃ or Y₂O₃, but it is also possible to conduct a high-speedflame spraying process or an explosion spraying process.

[0040] b. Formation of Undercoat, Middle Layer Through CVD Process orPVD Process

[0041] In the CVD process, steam of a halogen compound of a desiredmetal is reduced by hydrogen or the like and then oxidized by oxygen oran oxygen compound, and changed into an oxide film by heating in air.

[0042] In the PVD process, a sintered body or powder is used as astarting material and evaporated by irradiating an electron beam toprecipitate onto the surface of the substrate to form a film.

[0043] In general, the formation of the film through CVD process or PVDprocess is suitable for forming thin film (e.g. about 50 μm).

[0044] (5) Environment Using the Member According to the Invention

[0045] The Y₂O₃ sprayed coating covered onto the surface of the memberaccording to the invention is particularly useful for the use underplasma environment generated in an atmosphere containing a halogencompound.

[0046] Of course, the invention is effective even to a plasma erosionaction in an environment containing no halogen element or halogencompound such as N₂, H₂ or the like. In this case, erosion damagebecomes gentle as compared with the environment containing the halogenelement or compound, so that the sprayed coating member according to theinvention develops a stable performance over a long time.

EXAMPLE Example 1

[0047] In this example, a one-side surface of an aluminum test piece(size: width 50 mm×length 50 mm×thickness 5 mm) is roughened by a shotblast treatment and Y₂O₃ sprayed coating having a thickness of 300 μm isformed by using Y₂O₃ spraying material through a plasma spraying processunder an atmospheric pressure or a plasma spraying process under areduced pressure controlled to an atmosphere pressure of 50-200 hPa withAr gas, respectively.

[0048] And also, an undercoat of Ni-20% Al alloy is formed on a one-sidesurface of an aluminum test piece at a thickness of 100 μm by a plasmaspraying process under an atmospheric pressure and the above Y₂O₃ isformed thereon at a thickness of 300 μm as a top coat.

[0049] Thereafter, the porosity and adhesion strength of the Y₂O₃sprayed coating formed on the surfaces of these test pieces are measuredand thermal shock test (test of repeating a cycle of an operation thatthe piece is heated in an electric furnace held at 500° C. for 20minutes and cooled in air at the outside of the furnace 10 times) isconducted. Moreover, Al₂O₃ sprayed coatings formed under same conditionsat the same steps as mentioned above used as a comparative example.

[0050] The test results are shown in Table 1.

[0051] All of the coatings according to the invention, i.e. Y₂O₃ sprayedcoatings directly coated on the surface of the test piece (Nos. 1, 3)and Y₂O₃ sprayed coatings formed on the undercoat (Nos. 2, 4) show goodadhesion property and resistance to thermal shock, which are in no wayinferior to those of the Al₂O₃ film. Particularly, the Y₂O₃ coatingformed by the plasma spraying process under a reduced pressure issmaller in the porosity as compared with that of the coating formed bythe spraying process under an atmospheric pressure and can expect thegood corrosion resistance. TABLE 1 Structure of Visual coating Adhesionappearance Spraying Under Top Porosity strength in thermal No. Processcoat coat (%) (MPa) shock test Remarks 1 Atmospheric None Y₂O₃ 5 ˜ 9 35˜ 38 No peeling Example 2 plasma Ni-20Al Y₂O₃ 6 ˜ 8 38 ˜ 41 No peelingspray 3 Low None Y₂O₃ 0.2 ˜ 3   40 ˜ 41 No peeling 4 pressure Ni-20AlY₂O₃ 0.3 ˜ 4   40 ˜ 44 No peeling plasma spray 5 Atmospheric None Al₂O₃ 8 ˜ 12 38 ˜ 42 No peeling Compara- 6 plasma Ni-20Al Al₂O₃  9 ˜ 12 35 ˜44 No peeling tive spray Example 7 Low None Al₂O₃ 0.5 ˜ 5   38 ˜ 44 Nopeeling 8 pressure Ni-20Al Al₂O₃ 0.6 ˜ 7   39 ˜ 43 No peeling plasmaspray

Example 2

[0052] In this example, an aluminum substrate of 50 mm×100 mm×5 mmthickness is used and subjected to a surface treatment as shown in Table2 and a test piece having a size of 20 mm×20 mm×5 mm is cut out from thesubstrate and a portion is masked so as to expose the surface treatedface in a range of 10 mm×10 mm and irradiated for 20 hours under thefollowing conditions and measured is a damage quantity through plasmaerosion as a reduced thickness.

[0053] (1) Environmental Gas and Flow Rate Condition

[0054] A mixed gas of CF₄, Ar and O₂ is an atmosphere under thecondition.

CF₄/Ar/O₂=100/1000/10 (flow rate cm3 per 1 minute)

[0055] (2) Plasma Irradiation Output

[0056] High frequency power: 1300 W

[0057] Pressure: 133.3 Pa

[0058] The test results are shown in Table 2. As seen from the resultsof Table 2, the anodized film (No. 8) of a comparative example (existingtechnique) and B₄C sprayed coating (No. 10) are large in the damagequantity through the plasma erosion and are not put into practical use.Moreover, the Al₂O₃ coating (No.9) shows a relatively good resistance toplasma erosion among the comparative examples.

[0059] On the contrary, the Y₂O₃ sprayed coatings according to theinvention develop a very excellent resistance to plasma erosion andmaintain good performances even in an environment containing a halogencompound. TABLE 2 Damaged depth Presence of through Sprayed Surfaceabsence of erosion No. materials treatment undercoat (μm) Remarks 1 Y₂O₃(99.9%) Spraying Presence 6.2 Example 2 Absence 6.1 3 Y₂O₃ (99.8%)Spraying Presence 7.6 4 Absence 7.2 5 Y₂O₃ (99.5%) Spraying Presence 6.56 Absence 6.3 7 Y₂O₃ (99.9%) PVD Absence 6.6 Compara- 8 Al₂O₃ AnodizingAbsence 39.5 tive 9 Al₂O₃ Spraying Presence 8.1 example 10 B₄C SprayingPresence 28.0 11 Quartz — Absence 39.0

Example 3

[0060] In this example, 80% Ni-20% Al of 80 μm in thickness as anundercoat, Al₂O₃ or a mixture of Al₂O₃ 50 vol %/Y₂O₃ 50 vol % of 100 μmas a middle layer and Y₂O₃ of 200 μm in thickness are formed on analuminum substrate of width 50 mm×length 100 mm×thickness 5 mm by aplasma spraying process under an atmospheric pressure, respectively, andthen a plasma erosion test is carried out under the same conditions asin Example 2.

[0061] As a result, since the Y₂O₃ sprayed coating is formed on theoutermost surface layer portion (top coat), even when Al₂O₃ or themixture layer of Al₂O₃/Y₂O₃ is formed as the middle layer, theresistance to plasma erosion is not influenced in the sprayed coatingaccording to the invention and only a loss of 6.1-7.5 μm is observed byirradiation for 20 hours, and hence it is recognized to developsufficient performances even in the multilayer structure coating.

Example 4

[0062] In this example, with respect to a test piece obtained byanodizing the existing aluminum substrate (alumite treatment) and a testpiece formed by covering a 80% Ni-20% Al alloy coating of 100 μm inthickness on the substrate as an undercoat and coating a Y₂O₃ coating of250 μm in thickness thereon as a top coat through plasma sprayingprocess is carried out a plasma etching under the following conditionsto measure the number of particles flied through the etching as particlenumbers adhered onto a surface of a silicon wafer of 8 inches indiameter placed on the same chamber. Moreover, the number of particlesadhered is examined by a surface inspection apparatus based on particleshaving a particle size of not less than approximately 0.2 μm.

[0063] (1) Environmental Gas and Flow Rate Condition

[0064] A mixed gas of CHF₃, O₂ and Ar is an atmosphere under thecondition.

CHF₃/O₂/Ar=80/100/160 (flow rate cm3 per 1 minute)

[0065] (2) Plasma Irradiation Output

[0066] High frequency power: 1300 W

[0067] Pressure: 4 Pa

[0068] Temperature: 60° C.

[0069] As a result of this experiment, in the anodized test piece(alumite film), the particle number exceeds 30 particles as a particlecontrol value in the general chamber after 17.5 hours of the plasmairradiation and is not less than 150 particles after 25 hours. Thecomposition of the particle consists of Al and F.

[0070] On the contrary, in the Y₂O₃ sprayed coating according to theinvention, the particle number only exceeds the control limit value evenafter 70 hours of the irradiation and the excellent resistance to plasmaerosion is indicated.

[0071] Industrial Applicability

[0072] As mentioned above, according to the invention, the memberobtained by directly forming Y₂O₃ sprayed coating on the metallic ornon-metallic substrate or by forming a metallic undercoat and thenforming Y₂O₃ sprayed coating shows an excellent resistance when it isused under an environment subjected to plasma erosion action in a gasatmosphere containing a halogen compound. To this end, even when plasmaetching operation is continued over a long time, the contaminationthrough particles in the chamber is less and it is possible toefficiently produce a high quality product. And also, the contaminationrate of the particle in the chamber becomes slower, so that the intervalfor the cleaning operation becomes long and the improvement of theproductivity can be expected. As a result, the members according to theinvention are very effective as an internal member for a plasma treatingvessel in the field of semiconductor production apparatus, liquidcrystal device or the like.

1. An internal member for a plasma treating vessel comprising asubstrate and a Y₂O₃ sprayed coating covered on a surface thereof.
 2. Aninternal member for a plasma treating vessel comprising a substrate, ametal coating formed on a surface thereof as an undercoat, and a Y₂O₃sprayed coating formed on the undercoat as a top coat.
 3. An internalmember for a plasma treating vessel comprising a substrate, a metal filmformed on a surface thereof as an undercoat, a middle layer formed onthe undercoat and a Y₂O₃ sprayed coating formed on the middle layer as atop coat.
 4. An internal member for a plasma treating vessel accordingto claim 1, 2 or 3, wherein the metal coating as the undercoat is acoating of one or more metals or alloys selected from Ni and an alloythereof, W and an alloy thereof, Mo and an alloy thereof and Ti and analloy thereof and having a thickness of 50-500 μm.
 5. An internal memberfor a plasma treating vessel according to claim 1, 2 or 3, wherein themiddle layer is a layer of Al₂O₃ or a mixture of Al₂O₃ and Y₂O₃.
 6. Aninternal member for a plasma treating vessel according to claim 5,wherein the middle layer is formed by a layer having a gradientconcentration such that a concentration of Al₂O₃ is high at a side ofthe undercoat and a concentration of Y₂O₃ is high at a side of the topcoat.
 7. An internal member for a plasma treating vessel according toclaim 1, 2 or 3, wherein the Y₂O₃ sprayed coating is a coating having aporosity of 0.5-10% and a thickness of 50-2000 μm.
 8. A method ofproducing an internal member for a plasma treating vessel, whichcomprises covering Y₂O₃ on a surface of a substrate through a sprayingprocess to form a Y₂O₃ sprayed coating.
 9. A method of producing aninternal member for a plasma treating vessel, which comprises applyingat least one surface treating process selected from CVD process, PVDprocess and thermal spraying process to a surface of a substrate to forma composite layer consisting of a layer of a metal of Ni, W, Mo or Ti oran alloy thereof as an undercoat and Y₂O₃ as a top coat.
 10. A method ofproducing an internal member for a plasma treating vessel, whichcomprises applying at least one surface treating process selected fromCVD process, PVD process and thermal spraying process to a surface of asubstrate to form a composite layer consisting of a layer of a metal ofNi, W, Mo or Ti or an alloy thereof as an undercoat, Al₂O₃ or a mixtureof Al₂O₃ and Y₂O₃ as a middle layer and Y₂O₃ as a top coat.